Signaling system



Nov. 29, 1938. H, M, BASCOM. 2,138,565-

SIGNALING SYSTEM Filed April 30, 1937 RESISTANCE /vEaAr/VE F/G. 2

BVMWW A TTORNE Y Patented Nov. 29, 1938 UNITED STATES PATENT OFFICE SIGNALING SYSTEM Application April 30, 1937, Serial No. 139,924

7 Claims.

This invention relates to electrical signaling and particularly to signaling systems employing lamps or other devices for producing visual signals.

The objects of the invention are to secure improved operation in electrical signaling; to obtain additional functions from the lamps or other signaling devices; and in general to improve the construction of these signaling devices and to increase the usefulness of the systems in which they are employed.

It has been the practice in the past to provide telephone subscribers signaling circuits with pilot signals, Which are common to a number of individual line lamp signals. The pilot signal,

which operates to attract the o-perators attention Whenever one of the individual line lamps is illuminated, is usually connected in a circuit having parallel branches extending through the several individual line lamps to which it is common. kThe presence of the pilot signal, which may be a relay or a lamp, in the common circuit tends to limit the current and to interfere with the proper operation of the individual signals. Also it is diiicult to design a pilot device, such as a relay, that is sensitive enough to operate on one line signal and rugged enough to withstand the current when several line signals are burning.

According to the present invention improvements Aare obtained in signaling systems of the particular character above mentioned as Well as in signaling systems in general by the provision of a signaling lamp in which the luminous lament serves to give the usual visual signal and also to control an auxiliary circuit device. According to .a feature of the invention a signal lamp, such as a subscribers line lamp, is equipped with a luminous filament and With a small resistor of some material, such as boron, having a high temperature coeiiicient of resistance, the boron resistor being mounted Within the lamp bulb in proximity to the filament thereof and connected in circuit with a pilot relay or a pilot lamp common to a number of the line lamps, whereby the heat produced by the illumination of any one of the line lamps changes the resistance of the boron resistor individual thereto to cause the ow of suflicient current through the common pilot device to bring about the operation thereof. With this arrangement it is possible to operate the filaments of the subscribers line lamps in individual circuits freefrom the impedance of pilot devices. These individual circuits for lighting the line lamps may be local to the central oce or they may include the loops of the subscribers lines. The common pilot relay or lamp is connected in circuit with the several boron resistors, the initial or cold resistance of which is sufficiently high to prevent the flow of any appreciable current in the pilot circuit. When, however, any one of the lamps is lighted, its lament, as above explained, heats the associated resistor, producing a large drop in the resistance thereof and the consequent ow of enough current in the common pilot circuit to operate the pilot relay or the pilot lamp as the case may be.

The foregoing and other features of this invention will be described more fully in detail in the following specication. In the drawing accompanying this specification:r

Fig. 1 shows a portion of a telephone system in which subscribers lines are equipped with line lamps embodying the features of this invention;

Fig. 2 illustrates one of the individual line lamps o-f Fig. 1 and a modification of the common pilot circuit; and

Fig. 3 illustrates the invention applied to a system in Which the line lamps are lighted over the subscribers loops.

Each of the subscribers lines, such as the line |00, appears in the central oce in a suitable connecting device. The line |00 is shown terminating in an answering jack |02 and is provided with the usual individual line relay I 03 and cut-off relay |04. In addition the line |00 is equipped with an individual line lamp |05 mounted in any suitable position before the operator. The line lamp |05 of subscribers line |00, the line lamp |06 of a second subscribers line, and other lamps, not sho-Wn, are connected in circuit with a commo-n pilot relay |01. Pilot relay |01 controls the circuit of the pilot signal lamp |08. The operators position is equipped With the usual cord circuits, such as the cord |09 illustrated.

Referring to Fig. 2, the novel signal lamp which is there illustrated in enlarged form, comprises the usual glass bulb l0 and the luminous lament |I|. The filament is sealed Within the bulb ||0 and is connected to the exterior terminals ||2 and l! 3. Also sealed Within the glass bulb ||0 is a resistor H4 of some material having a high negative temperature coeflicient of resistance. It has been found that the element boron is especially Well suited to this purpose. It has an extremely high temperature coeflicient, it is hard and durable, and it does not deteriorate signal.

when subjected either to direct current or alternating current. Furthermore the required resistance Values can be obtained with boron units of small dimensions which occupy .a small amount of space and lend themselves readily to mounting within the restricted spaces available in signal lamps. For example, some of these units may have dimensions of the order oi 150 of an inch. The boron resistor H4 is mounted within the bulb HU in such a position that it is in close proximity to the filament This mounting arrangement places the resistor H4 in position to receive heat conveyed from the burning iilament One of the terminals of the resistor H4 is joined by a iine lead wire H5 to the terminal H2, and the other terminal of the resistor H4 is joined by a i'lne lead Wire I6 to a third exterior terminal H1. The terminals H2 and H3 of the lamp lament are connected respectively to the battery H8 and to ground through the operated contact of the subscribers line relay H9. Thus the line lamp ||ll is lighted in a circuit containing only the central oice battery and a contact of the line relay. The pilot device, such as the pilot lamp |20, is connected to the terminal H1. This connection includes the pilot lamp |29 in a circuit from the battery H3, terminal H2 through the resistor lid, terminal ||1 through the lament of lamp |20 to ground. The lamp |20, being common to a number o1 line lamps, is connected in multiple to the terminals ||1 of other line lamps. not

shown. Y

Since the pilot device, such as the relay |61 in Fig. l or the lamp |23 in Fig. 2, is connected in series-parallel relation with a plurality of the boron resistor units, it is necessary that the resistance of these units be high when they are cold so that the combined resistance of the several parallel circuits is sumciently high to prevent iiow of any appreciable current through the common pilot device. And this requirement is easily met with. boron units because of their extremely high normal resistance.

A brief description will now be given or" the manner in which the system of Fig. l operates. When the subscriber of line |58 initiates a call by removing his telephone receiver, the usual circuit is closed for the line relay m3. This relay operates and closes a circuit from ground through its armature and contact, through the lament |2| of line lamp |55 to battery. The filament |2| assumes an incandescent state and emits heat which is transferred to the boron resistor |22 mounted in proximity thereto. As the temperature of the resistor |22 rises, its resistance undergoes a large and rapid drop, permitting a substantial current to ow in the circuit from battery through the resistor |22, conductor |23, common pilot relay |01 to ground. The relay 31 operates in this circuit and closes an obvious circuit for lighting the pilot lamp |93 to attract the operators attention to the fact that the line lamp is lighted as a calling The operator answers the call by inserting the plug |24 of her cord. iii@ in the jack 502 of the calling line. 'Ihe insertion of the plug in the jack completes a circuit from battery through the supervisory lamp |25, resistance |25 through the sleeve of the plug and jack and the Winding of the cut-off relay Hifi to ground. The lamp, however, does not light because it is shortcircuited at the Contact of the supervisory relay |21, which is operated in a circuit from battery through the lower left Winding of the repeating coil |28, winding of relay |21, ring contacts of the plug and jack over the subscribers line loop and returning through the tip contacts of the jack and plug through the upper left winding of the repeating coil |23 to battery. The cut-off relay |04 operates and disconnects the line relay |03 from the subscribers line. Relay |03 releases and extinguishes the lament |2| of the line lamp. The boron unit |22 now cools and assumes its normal high resistance. This decreases the flow of current through the relay |01, provided this relay is not deriving current from some other line lamp, and the relay releases to extinguish the pilot signal H18. The operator completes the connection with the other plug |29 of her cord circuit, and, when conversation is over, she removes her cord circuit, permitting the cut-01T relay to release and reconnect the line relay |783 to the subscribers line.

Referring now to the modification of Fig. 3, the Vsystem here illustrated is one in which the individualV line and cut-off relays are omitted, and the line lamps are lighted in circuits including the loops of the subscribers lines. If the current for a number of these line lamps is supplied through a common pilot signal relay, there is a danger of ioperating the common 4relay falsely in the event that the line loops develop a substantial amount or" leakage. This, however, may be avoided by using the improved signal lamp and by connecting it as illustrated in Fig. 3. The lamps in this arrangement, like those in Fig. i, are supplied with current over circuits excluding the common pilot relay.V For example, the lamp |39 has its luminous filament i3! connected directly to the conductor |32 of the subscribers line |33l through a contact of the cutoff jack |34. The other conductor |35 of the subscribers line is connected through a Contact of the cut-oi jack to ground. Therefore, a closure of the line |33 at the substation completes a direct circuit for supplying current to the filament 53| of the lamp |38. In a similar manner the lamp |315, individual to the subscribers line |31 is lighted in a circuit extending from battery directly through the filament of the lamp and over the loop of the subscribers line.

The negative-resistance elements of the several line lamps, such as the elements it@ and iSiiof the two lamps shown, are connected to a common conductor |48, which may either extend to ground directly through a pilot lamp as illustrated in Fig. 2 or to ground through a pilot relay Mi. The cold resistance of these negative resistors is so high that substantially no current flows normally over the comme-n conductor lill) and through the relay Ml. And although any one of the subscribers lines |33, 31, etc. may have some leakage, resulting in a ilow of some current through the filament of the lamp of the leaking line and thence to ground, the amount of heat produced by this leaking current in the filament of the lamp is insuiicient to cause enough of a change in the resistance of the resistor within the lamp to enable enough current to flow in the common conductor |135 to operate the pilot relay. Some of these negative resistance materials are known to have critical points in their temperature-resistance characteristics, and they may, therefore, be designed so that they can receive and dissipate substantial amounts or" heat without exceeding the critical points in their characteristics beyond which their resistance decreases by large amounts.

To briefly .describe the operation of .the system of Fig. 3, assume that the subscriber at the substation of line |33 Wishes to make a call. When he removes his receiver from the svvitchhook, the loop is closed, and current ovvs from battery through the filament |3| of lamp |30, through the lower contact of jack |34 over the closed loop and returning to ground through the upper contact of said jack. The lament |3| is heated in this circuit to give the line lamp signal and to raise the temperature of the negative resistor |38. This lowers the resistance of the element |38, and substantial current now flows from battery through said resistor over conductor |40, through the winding of relay |4| to ground. Relay |4| operates and closes an obvious circuit for the common pilot lamp |42. The lamp |42 attracts the operators attention, and, observing the individual line lamp |30 burning, she knows that a call is Waiting on line |33. The operator, Whose position may be equipped With cord circuits similar to the one shown in Fig. l, responds by inserting the answering plug of one of her cords in jack |34. Insertion of the plug in the jack opens the cut-off contacts and severs the circuit through the filament of lamp I3 The lamp extinguishes, and the element |38 decreases its resistance to cause the deenergization of the common relay |4| and the eiacement of pilot signal |42, provided no other line is calling at the moment. From this point on the operation of the system continues in the Well-known manner.

While boron has been discussed herein as a suitable material for the resistors, it should be understood that the invention is not limited to any material and that other substances, such as silver sulphide, having suitable temperature coeilicients of resistance may be used. For a general disclosure of a resistance device having a negative temperature coeicient of resistance, reference is made to the patent to Grondahl, No. 1,526,139, of February l0, 1925.

What is claimed is:

1. The combination in a signaling system of a lamp comprising a closed chamber, a luminous filament within said chamber, a current carrying element mounted Within said chamber to receive heat fromV said lament, said element undergoing a change of its electrical characteristic when heat is received from said lament, electrical circuits including said filament and said element, and means in circuit With and dependent upon the electrical characteristic of said element.

2. The combination in a signaling system of a signal lamp comprising a glass bulb, a resistor, having a temperature coeicient of resistance, mounted Within said bulb and arranged to receive heat from said filament When lighted, a circuit including said resistor, and means in said circuit operable in response to a change in the resistance of said resistor.

3. The combination in a signaling system of a lamp comprising a closed chamber and three circuit terminals, a filament mounted within said chamber and connected to a pair of said terminals, a circuit connected to said pair of terminals for supplying current to heat said filament, a variable resistance element mounted Within said chamber to receive heat from said filament, said element being connected between one of the terminals of said pair and said third terminal, an electrical circuit including said variable resistance element, and means in said last-mentioned circuit operable in accordance with the resistance of said element.

4. The combination in a signaling system of a lamp having a closed chamber and a luminous filament therein, an element of boron mounted Within said lamp to receive heat from the luminous iilament, a normally deenergized relay connected in circuit with said boron element, and means ior heating said lament to alter the resistance oi said boron element and cause the operation of said relay.

5. The combination in a signaling system of a plurality oi signal lamps, each containing a luminous iilament and a variable resistance element arranged to receive heat from the associated lament, individual circuits for the respective luminous filaments of said lamps, a common circuit having branches including the respective variable resistance elements, an operating device in said common circuit, and means for heating any one of the luminous laments to cause a change in the resistance of the associated variable resistance element to cause the operation oi the device in said common circuit.

6. In combination, a telephone line, a signaling lamp having a closed chamber and a luminous filament therein, a circuit including the talking conductors of said line for supplying current to said lament, a resistor having a temperature coeicient of resistance mounted within said chamber and arranged to receive heat from said iilament When lighted, a circuit including said resistor, and means in said last-mentioned circuit operable in response to a change in the resistance of said resistor.

7. The combination in a telephone system of a plurality of subscribers lines, each line having a line relay and a signal lamp comprising a bulb With a luminous lament therein, energizing circuits for said laments closed, respectively, by the corresponding line relays` when energized, each of said lamp bulbs having a variable resistance element mounted therein to receive heat from the corresponding lament when the latter is energized, said elements undergoing a change of resistance in response to the heat received from their associated luminous laments, a common circuit including said variable resistance elements, and means in said common circuit operable in response to a change in the resistance of any one of said elements.

HENRY M. BASCOM. 

